document the phpcr_odm_reference_collection form type
Merge remote-tracking branch 'origin/master' into phpcr_odm_reference_collection
Added code example
Merge pull request #101 from symfony-cmf/phpcr_odm_reference_collection

document the phpcr_odm_reference_collection form type
added some hints about event subscribers
Merge remote-tracking branch 'origin/master' into document-phpcr-odm-image-formtype

Conflicts:
	bundles/phpcr-odm.rst